Controlling the spread of interests and content in a content centric network

ABSTRACT

One embodiment of the present invention provides a system for controlling the spread of interests and content in a content centric network (CCN). During operation, the system maintains a routing policy for content data. The system also receives a packet associated with a piece of content or an interest for the content. Next, the system determines that the structured name included in the packet is within the namespace specified in the routing policy. The system further determines that the packet satisfies the condition in the routing policy. Subsequently, the system routes the packet based on in part the action corresponding to the condition as specified in the routing policy.

RELATED APPLICATION

This application is a continuation of:

-   -   U.S. patent application Ser. No. 12/338,175 , entitled         “CONTROLLING THE SPREAD OF INTERESTS AND CONTENT IN A CONTENT         CENTRIC NETWORK,” by inventors Van L. Jacobson and Diana K.         Smetters, filed 18 Dec. 2008,         which claims the benefit under 35 U.S.C. § 119(e) to:     -   U.S. Provisional Patent Application No. 61/054,044 , entitled         “CONTENT-CENTRIC NETWORKING: POLICY ROUTING AND FIREWALLING,” by         inventors Van L. Jacobson and Diana K. Smetters, filed 16 May         2008,         the disclosures of which are incorporated by reference herein.

The subject matter of this application is related to the subject matter in the following applications:

-   -   U.S. patent application Ser. No. 12/123,344 , entitled “VOICE         OVER CONTENT CENTRIC NETWORKS,” by inventors Paul Stewart,         Van L. Jacobson, Michael Plass, and Diana K. Smetters, filed 19         May 2008; and     -   U.S. patent application Ser. No. 12/332,560 , entitled “METHOD         AND APPARATUS FOR FACILITATING COMMUNICATION IN A CONTENT         CENTRIC NETWORK,” by inventor Van L. Jacobson, filed 11 Dec.         2008.         the disclosures of which are incorporated by reference in their         entirety herein.

FIELD

The present disclosure relates generally to facilitating communication over a data network. More specifically, the present disclosure relates to a method for controlling the spread of interests and content in a content centric network.

RELATED ART

The proliferation of the Internet and e-commerce continues to fuel revolutionary changes in the network industry. Today, a significant number of information exchanges, from online movie viewing to daily news delivery, retail sales, and instant messaging, are conducted online. An increasing number of Internet applications are also becoming mobile. However, the current Internet operates on a largely location-based addressing scheme. That is, a consumer of content can only receive the content by explicitly requesting the content from an address (e.g., IP address) closely associated with a physical object or location. This restrictive addressing scheme is becoming progressively inadequate for meeting the ever-changing network demands.

The current architecture of the Internet revolves around a conversation model, which was created in the 1970s for the ARPAnet to allow geographically distributed users to use a few big, immobile computers. This architecture was designed under the influence of the telephone network, where a telephone number is essentially a program that configures the switches along a path from the source to the destination. Not surprisingly, the designers of the ARPAnet never expected it to evolve into today's ubiquitous, relentlessly growing Internet. People now expect a lot more from the Internet than what the ARPAnet was designed for. Ideally, an Internet user should have access to any content, anywhere, at any time. Such access is difficult to guarantee with the current location/device-binding IP protocol.

Under current web-based naming structures, an idea of the host is implicit in the name which contains the corresponding content. For example, http://www.amazon.com/index.html can be found by contacting the machine www.amazon.com. But this contact requires a Domain Name System (DNS) to translate a human-readable host name into an IP address (e.g., 209.34.123.178). In current computer systems, there is no way to refer to a piece of content without knowing what host that file is stored on, and even then the contents associated with that file might change.

Some computer systems use distributed hash tables (DHTs) to locate content by naming content with fixed-length keys, typically 160-bit opaque binary blobs. To retrieve a piece of content, a DHT-enabled system first obtains the content's “name,” and then uses a mapping from this name onto a set of servers in order to determine the server or servers from which the content might be retrieved.

DHT systems use opaque binary names that are treated as keys to indicate which host or hosts in a self-organizing ring of DHT hosts are responsible for holding that content. However, DHT names are not human-readable names. In addition, DHT systems assume a fully connected network, where content will always be found at a particular location based on in part the 160-bit opaque name.

DHT systems use opaque binary names that are treated as keys to indicate which host or hosts in a self-organizing ring of DHT hosts are responsible for holding that content. However, DHT names are not human-readable. In addition, DHT systems assume a fully connected network, where content will always be found at a particular location based on in part 160-bit opaque name.

Other computer systems in peer-to-peer networks typically find content by title either indirectly through a directory server (e.g., Napster), which maintains a lookup table that maps content names to hosts, or by flooding interest to all the hosts in the network, along with information about where to return matching results to the interest.

Content names in all of these approaches are “flat,” with no relationship contained in them other than perhaps what host holds them.

Protocol-Independent Multicast Sparse Mode (PIM-SM) is a protocol that allows routing content on-demand using tree-based routing. In PIM-SM, nodes interested in receiving particular IP multicast “channels” (represented as IP addresses drawn from the set designated for multicast) register to receive that content with a multicast-capable router or switch “upstream” from them. That router then recursively registers to receive that content. When the content is generated on that address, the routers can look at their various outgoing interfaces or switch ports for those where such interest has been registered, and forward the new content only on those.

PIM-SM and other forms of multicast routing only generate multicast trees over a small space of IP addresses and do not provide flow control. In other words, a single interest in content can open the floodgates for any and all available content, thus potentially drowning a network and causing multicasting to be disabled or throttled back. This is because PIM-SM and other forms of multicast routing do not cause an interest to be consumed when matching content is found.

SUMMARY

One embodiment of the present invention provides a system for controlling the spread of interests and content in a content centric network (CCN). During operation, the system maintains a routing policy for content data. The routing policy specifies a namespace, a condition, and a routing action corresponding to the condition. The namespace corresponds to one or more structured names, each of which is unique and persistent with respect to certain content. The namespace includes at least part of a content name which can be used to match content with a more specific name that falls logically within the scope of the name space. The condition specifies when the routing action can be taken upon receipt of data packets associated with the namespace. The system also receives a packet associated with a piece of content or an interest for the content. The content is identified by a structured name and the structured name in the packet includes authentication information for the content. Next, the system determines that the structured name included in the packet is within the namespace specified in the routing policy. The system further determines that the packet satisfies the condition in the routing policy. Subsequently, the system routes the packet based on in part the action corresponding to the condition as specified in the routing policy.

In one variation on this embodiment, the system determines that the structured name included in the packet is within the namespace by using a longest-name match policy to match the structured name against the namespace.

In one variation on this embodiment, routing the packet includes one or more of: dropping content packets, thereby preventing creation of content with a certain name; dropping interest packets, thereby preventing interests from circulating; forwarding the packet to another node; copying or redirecting the packet; deferring action on the packet; and applying a default policy when no conditions match.

In one variation on this embodiment, determining that the packet satisfies the condition includes matching one or more of: an identity of a signer of the content by using a public key, a credential held by a signer of the content; an identity of a node generating an interest by using a public key, a network interface on which the packet arrived, and a network address indicating where the packet is originated or destined.

In one variation on this embodiment, the system automatically retrieves keys and credential information (from the CCN) to check policy compliance, where the keys and credential information.

In one variation on this embodiment, the interest corresponds to a portion of the content system, sending the content to the interest owner comprises sending only a portion of the content to the interest owner, and continued receipt of interests of the same content facilitates flow control of the delivery of the content.

In one variation on this embodiment, the system stochastically verifies the routing policy by router nodes, thus enabling an overall expected level of policy compliance and verification.

In one variation of this embodiment, the system dynamically retrieves the policy from the CCN and dynamically updates the policy.

In one variation of this embodiment, the system defeats a denial-of-service attack against a policy enforcement system by greylisting keys so that automatic retrieval of keys is deferred.

In one variation of this embodiment, the system propagates the routing policy to an upstream node, whereby the upstream node can optionally enforce the routing policy and filter content.

BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 illustrates an exemplary CCN in accordance with an embodiment of the present invention.

FIG. 2 presents a flowchart illustrating the process of controlling the spread of interests and content in a CCN in accordance with an embodiment of the present invention.

FIG. 3 presents a flowchart illustrating the process of dynamically retrieving the policy from the CCN and dynamically updating the policy in accordance with an embodiment of the present invention.

FIG. 4 presents an exemplary computer and communication system for controlling the spread of interests and content in a CCN in accordance with an embodiment of the present invention.

DETAILED DESCRIPTION

The following description is presented to enable any person skilled in the art to make and use the invention, and is provided in the context of a particular application and its requirements. Various modifications to the disclosed embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be applied to other embodiments and applications without departing from the spirit and scope of the present invention. Thus, the present invention is not limited to the embodiments shown, but is to be accorded the widest scope consistent with the principles and features disclosed herein.

The data structures and code described in this detailed description are typically stored on a computer-readable storage medium, which may be any device or medium that can store code and/or data for use by a computer system. The computer-readable storage medium includes, but is not limited to, volatile memory, non-volatile memory, magnetic and optical storage devices such as disk drives, magnetic tape, CDs (compact discs), DVDs (digital versatile discs or digital video discs), or other media capable of storing computer-readable media now known or later developed.

Overview

A content centric network (CCN) brings a new approach to content transport. Instead of having network traffic viewed at the application level as end-to-end conversations over which content travels, content is requested or returned based on in part the name given to it, and the network is responsible for routing content from the provider to the consumer. Content includes data that can be transported in the communication system, including any form of data such as text, images, video, and/or audio. A consumer and a provider can be a person at a computer or an automated process inside or outside the CCN. A piece of content can refer to the entire content or a respective portion of the content. For example, a newspaper article might be represented by multiple pieces of content embodied as data packets. A piece of content can also be associated with metadata describing or augmenting the piece of content with information such as authentication data, creation date, content owner, etc. The present invention comprises a computer-implemented system to facilitate communication in a CCN. We will refer to the system interchangeably with the CCN, as the properties of the system are the properties of the CCN and vice versa.

A CCN can significantly improve the efficiency and usability of content dissemination by enabling content caching. A CCN can also improve content mobility by enabling content to move. This is because in a CCN content can be addressed by name rather than location.

In some embodiments, a CCN host can identify, request, and disseminate content based on in part the content's name, as opposed to a name of a content container, such as a file.

Unlike IP addresses, a content name does not necessarily indicate the location of the content, and the CCN is responsible for routing the content. In a CCN, content names are persistent and content-specific. That is, if one changes the content, the content is effectively associated with a new name. This persistency can be achieved with an explicit versioning mechanism, where, for example, the new content can be “version 4” of a given name. The persistency can also be achieved implicitly. For example, contents can be associated with not only their human-established names, but also with authentication meta-data (e.g., a digital signature by the publisher of the content). As a result, the name associated with content changes when the content change.

Functionally, a CCN can retain association between various names and the content which they represent. In one embodiment, the names are hierarchical and in many situations can be understood by a user. For example, “/abcd/bob/papers/ccn/news” could be the name of the content, i.e., the “news” article from the “ccn” collection of papers for a user named “Bob” at the organization named “ABCD.” In a CCN, there is no need for a content consumer to determine how to find the “ABCD” organization, or to find which host holds Bob's CCN publications from an application's perspective. Note that a content consumer is any entity, person, or machine that requests the content.

In one embodiment, to request a piece of content, a CCN node registers (e.g., broadcasts) an interest in that content by the content's name. An interest in a piece of content can be a query for the content according to the content's name or identifier. The content, if available in the network, is routed back to it by the host that stores the content. In one embodiment, the routing infrastructure intelligently propagates the interest to the prospective nodes that are likely to have the information and then carries available content back along the path which the interest traversed.

A CCN has additional properties which make it especially appealing. For example, all content can be cryptographically authenticated, meaning that some subset of nodes on the network (e.g., a legitimate querier of the content) can verify the authenticity of a piece of content. A CCN also allows content to be accessed by name, independent of its publisher.

At the same time, embodiments of the present invention can specialize requests for content by a certain publisher. For example, one can ask for “foo.txt,” or “foo.txt signed by Bob.” Any name forms can be agreed upon by and used as a contract between a producer and the consumer. For example, “self-verifying” names are a special class of names where the name itself directly identifies the content it refers to—for example, naming a piece of content by its cryptographic (e.g. SHA-1) digest. A user who has obtained the name can be certain that he has obtained the correct content for that name by verifying this correspondence. Furthermore, CCN permits a much wider range of authenticated name mappings, because the producer digitally signs their chosen name for the content along with the content itself. It is therefore possible to securely determine what content is “Bob's content for the name foo.txt” without having to use an opaque self-verifying name that must be securely transmitted. It is also possible to use hybrid self-verifying names, where some components (e.g. in one embodiment, the first component) of the name are for organization and efficient routing and may be user-readable, and the latter components of the name are self-verifying. In one embodiment, a CCN uses such names, wherein a respective CCN name includes a virtual self-verifying component as its last component. In addition, CCN allows the separation of content and trust, enabling different content consumers to use different mechanisms for establishing trust in the same piece of content. Although content might have been signed by a single publisher, it can be trusted for different reasons. For example, one user might trust a given piece of content because of a direct personal connection with its signer, whereas another user might trust the same content because of the content signer's participation in a public key infrastructure (PKI) which that user has chosen to trust.

FIG. 1 illustrates an exemplary architecture of CCN, in accordance with an embodiment of the present invention. In this example, a CCN 180 comprises CCN nodes 100-145. Each node in the CCN is coupled to one or more other nodes. Network connection 185 is an example of such a connection. The network connection is shown as a solid line, but each line could also represent sub-networks or super-networks which can couple one node to another node. CCN network 180 can be a local network, a super-network or a sub-network. Each of these networks can be interconnected so that a node in one network can reach a node in other networks. The network connection can be broadband, wireless, telephonic, satellite, or any type of network connection. A CCN node can be a computer system or an end-point representing users and/or devices that can generate interests or originate content.

In accordance with an embodiment of the present invention, a consumer can generate an interest in a piece of content and then send that interest to a node in CCN 180. The piece of content can be stored at a node in CCN 180 by a publisher or content provider, who can be located inside or outside the network. For example, in FIG. 1, the interest in a piece of content originates at CCN node 105. If the content is not available at the node, the interest flows to one or more nodes coupled to the first node. For example, in FIG. 1, the interest flows (interest flow 150) to CCN node 115, which does not have the content available. Next, the interest flows (interest flow 155) from CCN node 115 to CCN node 125, which again does not have the content. The interest then flows (interest flow 160) to CCN node 130, which does have the content available. The flow of the content then retraces its path (content flows 165, 170, and 175) until it reaches CCN node 105, where the content is delivered. Other processes such as authentication can be involved in the flow of content.

In CCN 180, any number of intermediate nodes (CCN nodes 100-145) in the path between a content holder (CCN node 130) and the interest generation node (CCN node 105) can participate in caching local copies of the content as it travels across the network. Caching reduces the network load for a second subscriber located in proximity to other subscribers by implicitly sharing access to the locally cached content. In FIG. 1, if CCN node 100 were to register an interest in the same content as CCN node 105, a locally cached copy of the content stored on CCN node 115 can satisfy the interest without traversing the entire content path all the way back to CCN node 130.

Furthermore, CCN 180 can provide better fault tolerance because content can be retrieved from multiple nodes if one node fails suddenly. In a CCN, a piece of content can be self-authenticating, which means that the content contains its own authentication. In one embodiment, each fragment of a piece of content can be digitally signed by someone trusted by the consumer so that it can be cached, replicated, and obtained from anyone and its integrity and authenticity confirmed.

In embodiments of the present invention, a CCN host combines self-authenticating content, names which are directly treated as content addresses, and the pairing of interests and data to provide flow control. This approach enables a dynamic, name-based communication protocol. Because of the dynamic routing of interests and content back to interested parties, the resulting network is resilient to node departure and network partition, and provides intrinsic mechanisms to facilitate node mobility. For example, CCN node 100 may migrate and become coupled with CCN node 105. Since CCN 180 finds content by name, a content provider can move from node to node while providing content, much as cell-phone user can move from cell to cell while communicating.

There are significant advantages to a CCN's dynamic name-based routing approach. First, in contrast to DHTs, a content producer has control over who is responsible for storing and providing its content. Other nodes in a CCN can cache that content and provide it as well, but the base nodes which serve as the initial source of content are determined by the default routes for a given name prefix. For DHTs, the node or nodes responsible for serving a particular piece of content are determined semi-randomly by which nodes end up responsible for what portion of the key space. Such nodes' policies and reliability are out of the control of the content producer, and their location might be suboptimal for content retrieval.

Second, security in a CCN is content-based: data can be stored anywhere, or retrieved from anyone. This results in higher data security and significantly increased network efficiency. Third, a CCN can operate in flow balance, providing inherent fairness, rate limitations, and dynamic response to changing network conditions.

A CCN has several properties. One property is that it attempts to maximize the number of nodes that can participate in the CCN by minimizing the expectations about those nodes. For example, by default CCN nodes are not expected to be trustworthy. This means that nodes are not in general reliable enough to enforce access control policies for others. Therefore, in one embodiment, data is expected to be self-protecting (e.g., encrypted) to prevent it from falling into unwanted hands. In general, CCNs operate without any centralized control. This means that anyone can write data to any name, any name can have multiple pieces of data associated with it (even created by the same publisher), and any piece of data can have multiple names.

Another property of the CCN is that a querier may receive multiple pieces of data in response to any interest. This means that it is up to the querier to determine which of the answers to the query is acceptable, according to the querier's own security and trust policies.

A node in the CCN can be made “smarter” (more controlling) by implementing policies that are more restrictive in terms of who can generate content under a given name and/or who can distribute interests and retrieve content under that name.

Smarter policies can create greater network efficiency by dropping unwanted traffic or “spam” on the path to a data consumer, rather than requiring the content to be filtered by the consumer. For example, a smarter policy can reduce congestion near the “last hop” to the consumer, which is typically of lower bandwidth than the paths leading up to that hop. Smarter policies can also limit what data gets into sensitive portions of the namespace and who can retrieve that data.

Overall System Operation

FIG. 2 presents a flowchart illustrating the process for controlling the spread of interests and content in a content centric network (CCN) in accordance with one embodiment of the present invention. During operation, the system maintains a routing policy for content data (operation 200). The routing policy specifies a namespace, a condition, and a routing action corresponding to the condition. The namespace corresponds to one or more structured names, each of which is unique and persistent with respect to certain content. The condition specifies when the routing action can be taken upon receipt of data packets associated with the namespace. The system also receives a packet associated with a piece of content or an interest for the content (operation 210). Next, the system determines that the structured name included in the packet is within the namespace specified in the routing policy (operation 220). The system then determines that the packet satisfies the condition in the routing policy (operation 230). After determining that the packet satisfies the condition, the system routes the packet based on in part the action corresponding to the condition as specified in the routing policy (operation 240).

Named Content

A CCN can associate names with content, where the names are persistent. The term “persistent” means that the content can move around, but the name stays with the content. In previous Internet communication models, if a content server dies and the content moves around, the name for the content (e.g., a universal resource locator, URL) must be changed. In a CCN, the content name remains unchanged. This enables an interest in a piece of content to find the content wherever it might reside.

The term “persistent” also means that if the content changes, then the name changes. The new name can be automatically generated as a version of the original name, can be associated with authentication metadata (e.g., a digital signature by the publisher of the content), or can reflect the nature of the content change.

Names in a CCN can be structured by dividing them into components. For example, in the name “/parc/home/smetters/test.txt,” the individual name components are parc, home, smetters, and test.txt. Note that “PARC” is an abbreviation of “Palo Alto Research Center,” an exemplary organization used in this disclosure. Structured names also enable efficient routing for named content. A component-wise structure allows a hierarchical organization of names, and a logarithmic efficiency in accessing content by name. There is no single “root” for a CCN naming scheme. However; the naming scheme can be modeled as a forest of trees. Names can be structured in various ways. For example, they can be structured in a left-oriented prefix-major fashion. For example, the name “/parc/home/smetters” can be a “parent” of “/parc/home/smetters/test.”

Name components can be binary strings and can be opaque to the underlying network. More generally, a semantic meaning to a name component is an agreement, or convention between name producers and consumers. Names can also be text or in a form where low-level CCN nodes can understand the meaning of “special” name components.

In sum, the system associates names (content identifiers) with content. Because of this naming convention, CCN content can be addressed, located, retrieved, cached, and disseminated by its name. In a CCN, obtaining content means publishing an interest in the name associated with the content. The CCN determines how to route information based on in part the name. Each time an interest is satisfied by content, the interest is erased, thus ensuring flow balance (never sending more data than is wanted). To receive another piece of content, the consumer must express another interest. Thus, a CCN pairs interests with content to provide efficient congestion control, which can be scaled automatically with the properties of network links, regardless of bandwidth.

Name-Based Routing Policy

Interests in, or queries for names can be satisfied (i.e., matched) in a prefix-oriented fashion. Name-based routing policies can be of various forms. One form is: if <condition> then <action>. Another form is a default routing policy, which states that if none of the conditions is matched, then a given default action is taken. Actions can include forwarding the packet as intended, dropping the packet, sending or copying the packet somewhere other than where it is intended to go, or deferring sending the packet to avoid downstream congestion.

CCN entities can include names, publishers (or, in the case of interests, consumers) and network interfaces. Publishers and consumers can be identified by their public keys or by meta-information associated with those public keys, such as who certified them. Network interfaces can be standard (e.g., cards that face onto a local Ethernet segment or wireless link). Network interfaces can also be virtual (e.g., pointing onto a multicast channel). CCN can also be implemented as an overlay network on top of the Internet Protocol (IP).

Policy conditions can include: when a given publisher P publishes content with a given name or name prefix N, when a given consumer C expresses an interest in a given name or name prefix N, when an interest for a name or name prefix N arrives or leaves on a given interface, when data for a given name or N arrives on a given interface, when a piece of content arrives, or when the time elapsed since the content was created has surpassed a predetermined threshold. Each of these conditions can include a particular interface on which the content or interest is sent.

An example policy is “only publisher P is allowed to publish content under the name prefix /PARC/home/P,” where publishers are identified by their public keys. Another example of a policy is “to publish under the name prefix /PARC, a publisher must have a key certified by the PARC certification authority.” The term “certified” can be in the traditional sense of having an X.509 certificate signed by a traditional certificate authority (CA). The term “certified” can also be an alternate form specific to CCNs, in terms of adding data to the CCN such that a trusted entity signs the mapping between a given name and the public key of a particular publisher. More generally, the term “certified” can refer to the publisher or consumer possessing any form of cryptographic or identifying credential of interest to the policy system. Details of these mechanisms are part of the key profile, or key distribution-related naming conventions, for CCNs.

In one embodiment, a CCN routing system uses a “longest-match” name-matching scheme. For example, an interest in “/parc/home/smetters” will match both “/parc/home/smetters/test.txt” and “/parc/home/smetters/bar.txt.” The longest match, in terms of the number of name components, is considered the best.

Thus, in a CCN, a router policy is a collection of rules, which map a condition to an action. The condition specifies a name or a name prefix, and optional condition clauses (e.g., restrictions on the signer of a name-content mapping, restrictions on the interface an interest or data item is traversing).

Rules in policy specifications are matched according to a longest-name match policy. Note that CCN names are structured objects. In one embodiment, names are structured in left-oriented prefix-major form). In other words, longer name matches override shorter ones in terms of what policy rules apply—a policy on the namespace prefixed by /parc.com/newuser/enroll would override one specified on /parc.com. Names can also be right-oriented or can have other forms of internal structure. The system can also use more complex name-matching methods.

Caching

In one embodiment, a CCN routing system can include a large cache. The cache can rapidly collect copies of all the public keys needed to verify the majority of frequent traffic. The cache enables the system to have a critical fast path through the router. Using cached keys and previously retrieved policy information, resolved data can fly through the router with minimal overhead. The system can further reduce overhead by using stochastic verification. Stochastic verification in this context means the system can check signatures on a probabilistic fraction of packets, where the fraction is dynamically determined by network load and perceived threat, and where the remaining packets are assumed to be correctly signed by who they claim to be signed by. The system can also determine the probabilistic fraction cooperatively among the organization's routers, to ensure that some node, but not every node, checks every packet. Similarly, the system can gain efficiency by verifying policy only where necessary—if an organization's routers trust each other to do their jobs, policy needs to be verified once, on the border or at the data ingress point, and not checked again.

Basic Policy and Router Defense

One policy that a CCN router can implement is to verify signatures on the CCN data itself. Without additional policy specifying who is “allowed” to write to a certain name, this simple verification for correctness ensures that the stated publisher (in the form of a specified public key) did indeed sign a particular piece of content.

The system's basic verification provides mechanisms for router defenses against denial-of-service attacks. The verification can also be stochastic, performed with a frequency determined by the perceived risk or level of detected attack. An attack might attempt to slow down or lock the CCN router by sending it a content signed by a number of different keys, which do not exist. Without a router defense, the router might attempt to retrieve those spurious keys and verify both the data and the properties of those keys (e.g., the entity that certified those keys) before deciding it can release that data. If an attacker can cause the router to be so bogged down by such outstanding requests, he can significantly degrade router performance.

To defeat such attacks, the system can use anti-chaffing techniques (where the spurious keys can be considered “chaff” among the “wheat” of correctly constructed keys and data). For example, if one sender sends a large number of randomly keyed data packets, the system can detect that and quarantine that sender. The system can also greylist new keys—hold them in abeyance temporarily, and retrieve them and verify associated data only when resources are available to do so. This enables the system to prevent greylisted keys and data from impacting the throughput of data signed by known senders, while creating minimal impact on temporarily greylisted data of new, legitimate senders.

Router Policy Efficacy

One issue with policy routing is that policy routing is only enforced by cooperating routers; consumers cannot rely on policy routing to completely protect them from unwanted data on either the local broadcast network or while they are roaming to networks outside of a managed infrastructure. However, policy routing can both protect an infrastructure from internal chaff, and significantly reduce the load on end nodes. The system can also further enforce organizational policy by having end nodes themselves implicitly enforce that policy over the applications local to that node (e.g., to control what names those applications write to).

Interest Signing

Policy routing can control who can insert data into a given namespace by limiting who is allowed to sign and propagate certain name-data mappings. The system can further control the network by requiring interest packets to be signed. The same namespace-based policies used to control forwarding of data packets can be used for interests as well. Alternatively, the system can apply separate (consumer and publisher) policies to interests and data.

Interest signing has several properties related to the space of potential policies. First, a policy can require all interest packets to be signed and therefore, in effect, require a “license to send” for any packet sent over a given network. Without an appropriate credential (e.g., the equivalent of a digital certificate), a sender cannot send either interest or data packets, and as those are the only possible packets to send in a CCN world. The result is, in effect, port-based access control for CCNs, which can allow control over who can connect to a given network port (e.g., hardwired network port or virtual wireless port) and send traffic over it. This immediately prevents unauthorized devices from transmitting any packets on the network beyond the local broadcast range. It also prevents such transmission in the equivalent of a switched network for CCNs, where a policy-enforcing network device (analogous to a CCN switch) resides between end nodes and prevents an unauthorized node from sending any packets to the network.

The system can also use interest signing to control who can obtain certain data items from the CCN. In general, access control in a CCN can be enforced by encryption, as one can get data packets from anywhere they happen to be cached. In general, CCN nodes are not trusted and are not expected to enforce an access control policy. However, in the case of a cooperating infrastructure router, a CCN node can be trusted to enforce an access control policy, and to drop interests in a part of a given namespace by anyone unauthorized to view that data. As described before, a policy can be matched by a longest-match of a name-action pair.

To make such a policy effective and to prevent people from requesting data over a local broadcast domain from their immediate peers, and from overhearing the response to such a request by an authorized peer, the system can assume the equivalent of a “switched CCN network” (see above), where end nodes do not see each other's immediate traffic, or where some of their traffic can be sent on channels other than the local broadcast channel.

In general, all sensitive data on a CCN can be encrypted. Encryption provides an additional layer of defense by keeping encrypted data from falling into the wrong hands.

The system can forward only appropriately signed interests and can choose not to combine interests unless the signers are equivalent from the point of view of the policy. The system can also use less verbose policies on interest signing, avoid aggregating signed interests, and drop interests on protected namespaces. The system further can avoid complex behavior, which is likely to result in unwanted and unexpected consequences.

Dynamic Policies and Policy Configuration

The system can use three features of CCN router policy to facilitate configuration and management. First, the CCN router can distribute a router policy by means of the CCN itself. A router, on encountering the first packet referencing a new namespace, can attempt to retrieve any available policy for it for that namespace via the CCN. The router can also automatically express an interest in and receive updates to its existing policies.

FIG. 3 presents a flowchart illustrating the process of dynamically retrieving the policy from the CCN and dynamically updating the policy in accordance with an embodiment of the present invention. During operation, the system dynamically retrieves the policy from the CCN (operation 300) and then dynamically updates the policy (operation 310).

Second, it can use cooperative policy enforcement. That is, if all the routers inside an organization are expected to trust one another, they can avoid re-checking each other's work. The system can also stop the propagation of undesirable data by enabling the first router identify and drop the undesirable data, provided the first router that receives the undesirable data is aware that the data is from an entity that is not a trusted router. A “trusted router” can also be an enterprise-configured CCN network stack on any participating node.

Third, the state can be distributed: a policy needs only be specified for those routers that need to know the policy. That is, a policy state needs only to be configured where it will be applied. For example, a policy about data accessible to a customer needs only to live and be maintained on the customer-facing CCN router. This enables easy configuration and management of the router policy.

Fourth, state and policy can be dynamic and data-dependent. As in current state-dependent firewalls, a router's content or interest filtering policy can depend on data or interests (rather than policy statements per se) it has previously seen, or which are made available to the CCN. For example, a state-dependent firewall can allow passage of responses to packets generated inside the firewall and traveling out, but not other inbound packets. Similarly, a CCN policy router can allow stateful “conversations” to pass as a function of the initial packets seen. Policies can be digitally signed, and if distributed can be automatically digitally signed as CCN data, which prevents malicious and unwanted attacks against the policy and routing infrastructure. In this way, the policy-based routing can in effect defend itself.

Policy Errors

Specifically, the system can authenticate name-content associations, rather than just content. For example, what a publisher claims when it inserts content into a CCN is “N is my name for content C.” A content publisher can digitally sign the mapping from the name N to the content C. The complete name of a piece of CCN content is the name along with the signature on that name, and content along with a certain amount of additional authentication metadata (e.g., an identifier of the publisher, such as the cryptographic digest of his public key, a timestamp, and a representation of the type of the content).

A router-focused policy, if incorrectly specified, can make data disappear so that it is invisible to users. CCNs, however, are more resilient to black-holing of data than traditional networks because data can follow multiple paths. For example, if one router in between drops data because of a bad policy, the system can route around that router.

Consumer-Specified Policy

The system can create and maintain policy-based filtering by and on behalf of an infrastructure (such as a corporation, on its internal LAN). The system can also use a policy to help end nodes defend against denial-of-service attacks by propagating a node's own policies “upstream” to the nodes serving them data.

Each end node (data producer or consumer) knows its own policies for accepting data, and can verify and appropriately determine whether to trust all the data it receives. However, if a node has a narrow bandwidth connection over which to receive that data, it is at risk of denial of service. A correctly behaving node upstream from an end node can filter content on the end node's behalf, but only if the end node trusts the upstream node to do the filtering and the upstream node knows what policy to apply. The end node can transmit cooperative policy statements to the node upstream from it, which that node might choose to use to pre-filter the data it receives before sending it down to the end node. In effect, the policy of the end node can cooperatively spread to those nodes upstream to it, which can opt (optionally as a function of contractual agreement) to enforce and filter on the end node's behalf. It is not possible to do this today, because there is no common way of naming policies so that the end node can publish them in a way that upstream nodes can consume them.

Policy Firewalling

A special-purpose name-based policy (i.e., a policy firewall) can reside on the “perimeter” of an organization and separates data coming from “inside” from data coming from “outside” (where inside and outside are defined by the administrator of this particular policy-enforcing node). Such a policy can keep illegitimate data that should normally only come from “inside” from passing to the “outside” (e.g., names under the/local namespace, analogous to non-routable addresses in IP). This special-purpose name-based policy can also keep data in recognized sensitive internal namespaces from traveling out without going through a VPN (Virtual Private Network) or other privacy-preserving transport.

Because interests can be drawn through a particular CCN node merely by expressing interests in those interests, such a policy firewall can be constructed more flexibly in terms of its location in network topology than can a traditional firewall.

Moreover, the policy firewall does not need to be on the direct path between two communicating nodes: it can be distributed among multiple nodes and combined to form a firewall as needed. Such policy-based firewalling can be used to defend any physical or virtual perimeter—e.g. an individual node, or a virtual collection of hosts or even content, independent of where that content lives, as long as all the routers servicing requests to that content participate in enforcing the policy.

Computer and Communication System

FIG. 4 presents an exemplary computer system for controlling the spread of interests and content in a CCN in accordance with an embodiment of the present invention. In FIG. 4, a computer and communication system 400 includes a processor 410, a memory 420, and a storage device 430, all of which are coupled together. Storage device 430 stores programs to be executed by processor 410. Specifically, storage device 430 stores a program 440 that implements a system (application) for controlling the spread of interests and content in a CCN 480.

Computer and communication system 400 can reside on any node in the CCN. During operation, CCN control application 440 is loaded from storage 430 into memory 420 and executed by processor 410. As a result, computer and communication system 400 performs the functions described above.

Computer and communication system 400 is coupled to an optional display 470, keyboard 450, and pointing device 460. Computer and communication 400 is also coupled to CCN 480, through which it receives and routes content, interests, and policies.

The methods and processes described in the detailed description section can be embodied as code and/or data, which can be stored in a computer-readable storage medium as described above. When a computer system reads and executes the code and/or data stored on the computer-readable storage medium, the computer system performs the methods and processes embodied as data structures and code and stored within the computer-readable storage medium.

Furthermore, the methods and processes described below can be included in hardware modules. For example, the hardware modules can include, but are not limited to, application-specific integrated circuit (ASIC) chips, field-programmable gate arrays (FPGAs), and other programmable-logic devices now known or later developed. When the hardware modules are activated, the hardware modules perform the methods and processes included within the hardware modules.

The foregoing descriptions of embodiments of the present invention have been presented for purposes of illustration and description only. They are not intended to be exhaustive or to limit the present invention to the forms disclosed. Accordingly, many modifications and variations will be apparent to practitioners skilled in the art. Additionally, the above disclosure is not intended to limit the present invention. The scope of the present invention is defined by the appended claims. 

What is claimed is:
 1. A computer-executed method for controlling the spread of interests and content in a content centric network, comprising: receiving a packet including a piece of content or an interest for the content, wherein the packet further includes a hierarchically structured name of the content; identifying, using a longest-matching lookup of the hierarchically structured name of the content, a routing policy applicable to a longest matching prefix of the hierarchically structured name, wherein the routing policy specifies a condition associated with an originating entity or a destination entity of the packet, and a forwarding action corresponding to the condition; in response to determining that the prefix matches the hierarchically structured name of the content and that the originating entity or the destination entity of the packet satisfies the condition in the routing policy, forwarding the packet according to the forwarding action specified in the routing policy; in response to determining that the originating entity or the destination entity of the packet does not satisfy the condition in the routing policy, forwarding the packet according to a default forwarding action; and defeating a denial-of-service attack against a policy enforcement system by greylisting a public key held by a signer of the content so that automatic retrieval of the public key is deferred.
 2. The method of claim 1, wherein the forwarding action comprises one or more of: dropping content packets, thereby preventing creation of content with a certain name; dropping interest packets, thereby preventing interests from circulating; forwarding the packet to another node; copying or redirecting the packet; and deferring action on the packet.
 3. The method of claim 1, wherein determining that the originating entity or destination entity of the packet satisfies the condition comprises matching an identity of the signer of the content by using a credential held by the signer of the content.
 4. The method of claim 1, wherein determining that the originating entity or destination entity of the packet satisfies the condition comprises matching an identity of a node generating the interest by using the public key.
 5. The method of claim 1, wherein determining that the originating entity or destination entity of the packet satisfies the condition comprises matching a publisher of the content or a consumer of the content.
 6. The method of claim 1, wherein determining that the originating entity or destination entity of the packet satisfies the condition comprises matching one or more of: a network interface on which the packet arrived; and a network address indicating where the packet is originated or destined.
 7. The method of claim 1, further comprising stochastically verifying the routing policy by router nodes, thus enabling an overall expected level of policy compliance and verification.
 8. The method of claim 1, further comprising propagating the routing policy to an upstream node, whereby the upstream node can optionally enforce the routing policy and filter content.
 9. An apparatus for controlling the spread of interests and content in a content centric network, comprising: a processor; and a memory, wherein the processor is configured to: receive a packet including a piece of content or an interest for the content, wherein the packet further includes a hierarchically structured name of the content; identify, using a longest-matching lookup of the hierarchically structured name of the content, a routing policy applicable to a longest matching prefix of the hierarchically structured name, wherein the routing policy specifies a condition associated with an originating entity or a destination entity of the packet, and a forwarding action corresponding to the condition; in response to determining that the prefix matches the hierarchically structured name of the content and that the originating entity or destination entity of the packet satisfies the condition in the routing policy, forward the packet according to the forwarding action specified in the routing policy; in response to determining that the originating entity or the destination entity of the packet does not satisfy the condition in the routing policy, forward the packet according to a default forwarding action; and defeat a denial-of-service attack against a policy enforcement system by greylisting a public key held by a signer of the content so that automatic retrieval of the public key is deferred.
 10. The apparatus of claim 9, wherein while forwarding the packet, the processor is configured to perform one or more of the following operations: dropping content packets, thereby preventing creation of content with a certain name; dropping interest packets, thereby preventing interests from circulating; forwarding the packet to another node; copying or redirect the packet; and deferring action on the packet.
 11. The apparatus of claim 9, wherein while determining that the originating entity or destination entity of the packet satisfies the condition, the processor is configured to match an identity of the signer of the content by using a credential held by the signer of the content.
 12. The apparatus of claim 9, wherein while determining that the originating entity or destination entity of the packet satisfies the condition, the processor is configured to match an identity of a node generating the interest by using the public key.
 13. The apparatus of claim 9, wherein while determining that the originating entity or destination entity of the packet satisfies the condition, the processor is configured to match a publisher of the content or a consumer of the content.
 14. The apparatus of claim 9, wherein while determining that the originating entity or destination entity of the packet satisfies the condition, the processor is configured to match one or more of: a network interface on which the packet arrived; and a network address indicating where the packet is originated or destined.
 15. The apparatus of claim 9, wherein while determining that the originating entity or destination entity of the packet satisfies the condition, the processor is configured to verify stochastically the routing policy by router nodes, thus enabling an overall expected level of policy compliance and verification.
 16. The apparatus of claim 9, wherein the processor is further configured to propagate the routing policy to an upstream node, whereby the upstream node can optionally enforce the routing policy and filter content.
 17. A computer-readable storage device storing instructions that when executed by a computer cause the computer to perform a method for controlling the spread of interests and content in a content centric network, the method comprising: receiving a packet including a piece of content or an interest for the content, wherein the packet further includes a hierarchically structured name of the content; identifying, using a longest-matching lookup of the hierarchically structured name of the content, a routing policy applicable to a longest matching prefix of the hierarchically structured name, wherein the routing policy specifies a condition associated with an originating entity or a destination entity of the packet, and a forwarding action corresponding to the condition; in response to determining that the prefix matches the hierarchically structured name of the content and that the originating entity or destination entity of the packet satisfies the condition in the routing policy, forwarding the packet according to the forwarding action specified in the routing policy; in response to determining that the originating entity or destination entity of the packet does not satisfy the condition in the routing policy, forwarding the packet according to a default forwarding action; and defeating a denial-of-service attack against a policy enforcement system by greylisting a public key held by a signer of the content so that automatic retrieval of the public key is deferred.
 18. The storage device of claim 17, wherein routing the packet comprises one or more of: dropping content packets, thereby preventing creation of content with a certain name; dropping interest packets, thereby preventing interests from circulating; forwarding the packet to another node; copying or redirecting the packet; and deferring action on the packet.
 19. The storage device of claim 17, wherein determining that the originating entity or destination entity of the packet satisfies the condition comprises matching an identity of the signer of the content by using a credential held by the signer of the content.
 20. The storage device of claim 17, wherein determining that the originating entity or destination entity of the packet satisfies the condition comprises matching an identity of a node generating the interest by using the public key.
 21. The storage device of claim 17, wherein determining that the originating entity or destination entity of the packet satisfies the condition comprises matching a publisher of the content or a consumer of the content.
 22. The storage device of claim 17, wherein determining that the originating entity or destination entity of the packet satisfies the condition comprises matching one or more of: a network interface on which the packet arrived; and a network address indicating where the packet is originated or destined.
 23. The storage device of claim 17, wherein the method further comprises stochastically verifying the routing policy by router nodes, thus enabling an overall expected level of policy compliance and verification.
 24. The storage device of claim 17, wherein the method further comprises propagating the routing policy to an upstream node, whereby the upstream node can optionally enforce the routing policy and filter content. 